Update to Minecraft 1.21.8, add checkstyle, fix compilation errors

- Update Paper API: 1.20.1 -> 1.21.4
- Update plugin version: 1.5.5-1.20.1 -> 1.5.5-1.21.8
- Add checkstyle plugin with reasonable rules
- Fix Enchantment.LUCK -> Enchantment.UNBREAKING
- Fix EntityType.FIREWORK -> EntityType.FIREWORK_ROCKET
- Remove unused imports
- Add temp_*/ to .gitignore
- 118 files changed, 1633 insertions(+), 1301 deletions(-)

src/main/java/com/loki/lochat/commands/ClearChatCommand.java

@@ -24,7 +24,7 @@ public class ClearChatCommand implements CommandExecutor {
             for (int i = 0; i < com.loki.lochat.utils.Constants.CLEAR_CHAT_LINES; i++) {
                 player.sendMessage("");
             }
-            
+
             // Уведомление (если включено)
             if (plugin.getConfigManager().isClearChatMessageEnabled()) {
                 String message = plugin.getConfigManager().getClearChatMessage();